Frister & Rossman Cub7 Sewing Machine?

Frister & Rorsman Cub 7 sewing machine. There was a whirring noise and a snap from the top of the auto clutch area and now the needle does not work. I can manually wind the clutch and the needle does sew, but it does not work automatically. I've unscrewed the screw on the right side plate where clutch is housed, but cannot take the casing off as it is secured at the top. Found a 1" plastic ring that has fallen off something. If there is a drive belt, I think it has broken or come adrift. Can you help at all?